Method of blasting using explosive
slurries made at the blasting site



United States Patent 3,344,743 METHOD OF BLASTING USING EXPLOSIVESLURRIES MADE AT TI-m BLASTING SITE George L. Grilfith, Coopersburg,Pa., assignor to Trojan Powder Company, Allentown, Pa., a corporation ofNew York Filed Aug. 16, 1966, Ser. No. 572,793 8 Claims. c1. 1o2 23 Thisinvention relates to a method of blasting using explosive slurriescontaining a polyalkylene polyamine sensitizer made in situ fromnon-explosive starting materials at the blasting site or in closeproximity thereto, ready immediately after preparation for delivery to adesired location for detonation.

The use of slurried explosives based on ammonium nitrate, sodiumnitrate, and like inorganic oxidizers, together with a fuel, such asfuel oil, and optionally an explosive sensitizer, such astrinitrotoluene, nitrostarch and like materials, has recently gainedwide acceptance. These slurries are inexpensive, compared to manypreviously available materials, and are readily loaded in bore holes, inwhich location they can be used without undue danger of waterinsensitization. Aqueous explosive slurries of this type are describedin US. Patents Nos. 2,930,685 to Cook and Farnam, patented Mar. 29,1960, 3,083,127 to Griffith and wells, patented Mar. 26, 1963, 3,216,872to F. B. Wells, patented Nov. 9, 1965, 3,147,163 to Griffith and Wells,patented Sept. 1, 1964, and 3,121,036 to Cook et al., patented Feb. 11,1964.

Slurried explosives have, however, the disadvantage of having arelatively large volume, and an increased weight, as compared to dry,powdered formulations, due to the presence of the slurrying water. Ithas, accordingly, been proposed in U.S. application Ser. No. 315,908,filed Oct. 14, 1963, to Robert B. Clay, Douglas H. Pack, L. L. Udy, andM. A. Cook, and now abandoned, referred to in South African patent No.64/ 4,735, filed Oct. 5, 1964, that such slurried explosives be preparedat the site by mixing and delivering the explosive materials there,pumping them directly into the bore hole from the mixing equipment. Thisobjective is achieved, in accordance with that application, by simplyadapting on a truck or other mobile device the mixing equipment that isnormally used in the explosive plant for combining the ingredients of anexplosive slurry, with the exception that it is now no longer necessaryto package the slurried explosive, but it can be pumped directly fromthe mixer into the bore hole.

A loading system analogous to that described in this US. patentapplication and South African patent was used in 1961 by theIntermountain Research and Development Company, as reported in WorldMining, October 1965, pages 33 to 37, and 91. This system was improvedin 1962 by the use of field mixing and loading, using a pump truck,which was indicated to have several advantages over the prior pumploading system. It is asserted that when bulk slurry is formulated in aplant and force pumped into the drill hole, two serious problems areimposed. Firstly, in order to extrude the premixed slurry through a longhose, as required by the nature of many mines, it may often be necessaryto increase the water content above the optimum range. Secondly, theexplosive sensitizer requirement of the slurry might have to beincreased, in order to cope with the desensitizing effect of the excesswater. This means that in order to obtain optimum sensitivity, it isnecessary to keep on hand quantities of explosive sensitizer, forblending with the slurry in the desired amount, when the slurry isdiluted with additional water. It is, of course, undesirable to havelarge amounts of explosive sensitizer on hand at a mine site, but thisdisadvantage is not overcome, either, by the use of mixing and loadingequipment, because these simply premix the slurry with the sensitizer atthe site, and also require a storage supply of explosive sensitizer, inaddition to storage supplied of other explosive components, such as theinorganic nitrate and fuel.

In accordance with the instant invention, storage of explosivesensitizers at the blasting site is avoided entirely by forming thesensitized explosive slurry together with the polyalkylene polyamine asthe sensitizer in situ at the site, starting from non-explosivematerials. In consequence, not only are the starting materials safe tohandle, but the reaction is carried out under conditions such that thereaction fixture itself is safe and insensitive during the reaction, sothat there is virtually no likelihood of accidental detonation at anystage, even up to the moment the slurry is loaded into the bore hole.

The process in accordance with the invention of blasting usingpolyalkylene polyamine sensitized explosives made in situ proximate tothe blasting site from nonexplosive starting materials, comprises mixingand reacting formaldehyde and an ammonia-containing compound in analkaline reaction medium, and which also functions as a desensitizingagent for the polyalkylene polyamine sensitizer produced. This reactionmedium is preferably water, or is miscible with or dilutable with water,so as to form a homogeneous slurry medium for the resulting explosivecomposition. Following preparation of the polyalkylene polyamineexplosive sensitizer, which may contain unreacted formaldehyde andmethanol, in addition formulation of the slurried explosive is completedby incorporating any additional components, such as inorganic oxidizerand fuel, together with any additional slurrying medium, if necessary,after which the finished slurry can be brought into the bore hole or toany other blasting site.

It is to be understood that the term ammonia-containing compoundincludes ammonia and any ammonium compound such as ammonium nitrate,ammonium hydroxide, ammonium halides, ammonium sulfate, ammoniumphosphate, and the like.

If desired, formaldehyde can also be prepared in close proximity to theblasting site for use in the formation of the polyalkylene polyamine,starting from methanol and air, by use of a suitable catalyst, using anyof the known procedures, preferably one giving a reaction productcontaining a high proportion of methanol, such as the Hooker process,using a silver catalyst, Formaldehyde, third edition, by Walker(Reinhold Publishing Corp. 1964), pp. 17-19.

It is preferred in the practice of the instant invention that ammoniumnitrate be employed as the ammonia-containing compound, in an amount inexcess of that needed stoichiometrically to react with the formaldehyde,so that excess unreacted nitrate at the conclusion of the reactionremains in the reaction mixture, and serves as an oxidizer in theslurried explosive formulation. Such a slurry can accordingly becompleted simply by addition of fuel, and and any required slurryin-gmedium.

As reaction media, water and fuel oil or liquid parafiin hydrocarbonsare prefer-red. The latter serve not only as slurrying media, but alsoas fuels.

The apparatus in accordance with the invention includes, in combination,a reactor in which reaction to form the polyalkylene polyamine explosivesensitizer is carried out, and in which blending of the other componentsof the slurry, following completion of the reaction, or in the course ofthe reaction, can also be effected, and pumping equipment and relateddelivery means for delivering the finished slurry to the blasting sitewhere it is to be detonated. The reactor preferably includes stirringmeans for assisting in the reaction, and in the formulation of the isfinished slurried explosives, together with heating means, if required,and means to mix and deliver the reactants as well as the finishedslurry. Optionally, a reactor suitable for forming formaldehyde frommethanol and air can be combined in the apparatus.

To facilitate use of the equipment by large-scale users, the inventionalso contemplates equipment adapted for the continuous mixing andreacting of the reactants to form the polyalkylene polyamine explosivesensitizer, means for continuously delivering the reaction medium,including the explosive sensitizer, to a separate site at which mixingwith additional slurry components can be completed, and means forcontinuously delivering the resulting formulation to the blasting site.

It will be apparent that in this way the invention combines all of theadvantages of on-site mixing of slurried explosives, and in addition hasthe advantage that no storage of explosive sensitizers at the blastingsite or in the vicinity thereof is required. Explosive sensitizers canbe prepared in the amounts desired for immediate use at any time, andcan be used immediately after preparation.

The figure shows schematically a preferred embodiment of apparatus whichcan be used in carrying out the process of the invention, mounted on amobile vehicle to facilitate movement of the apparatus to any desiredblasting site.

As has been indicated, the process of the invention finds its greatestutility in the formulation and use at the blasting site of sensitizedslurried explosives, in which the polyalkylene polyamine sensitizer isprepared from an excess of ammonium nitrate. Hexamethylenetetramine,heptamethylene pentamine, octamethylene hexamine, and like polyalkylenepolyamines which are readily prepared in aqueous solution by reaction offormaldehyde (formed from methanol) and ammonium nitrate, are,accordingly, preferred explosive sensitizers for preparation inaccordance with the invention.

The process by which formaldehyde or the polyalkylene polyamines can beprepared forms no part of the instant invention, which merely employssuch processes for preparation of formaldehyde or the explosivesensitizer as one step in the combination of steps that facilitate anonsite blasting operation. Thus, for example, formaldehyde can be formedin close proximity to the blasting site from methanol prior to theformation of the polyalkylene polyamine, by passage of the methanol andair over a heated metal catalyst, such as platinum, copper or brassgauze, silver, gold, vanadium oxide, aluminum phosphate, and the like,Formaldehyde, pages 8 to 24, the disclosure of which is herebyincorporated by reference. In addition, the formaldehyde can be preparedfrom methane, propane and the hydrocarbon mixtures encountered innatural gas, or from butane, as is well known in the art.

The preferred methods of preparing formaldehyde in the process of theinstant invention are those which are safe, can be easily controlled,and which ordinarily will not cause explosions. In the preferred method,methanol is fed to a vaporizer to produce methanol vapor at 85 C. and 18p.s.i. This vaporizer maintains continuous delivery at the required ratethrough a superheater. Air is drawn in through a filter and a scrubbingcolumn where it is washed with caustic soda to remove carbon dioxide andsulfurous compounds since the latter are stated to be injurious tocatalyst activity. The air is then heated to about 70 C. and mixed incontrolled ratio with methanol vapor. The mixture which containsapproximately one volume of air for each volume of methanol vapor isfiltered and fed to the reactors which contain a bed of prepared silvercatalyst. These reactors operate in the range 450 to 650 C., thepreferred temperature being around 635 C. Gases from the reactor burnersare dissolved in water to produce a 20 to 37% formaldehyde solution. Thegases contain about 28 to 30% formaldehyde and 20 to 22% methanol. Themethanol-containing formaldehyde solution is fed to a storage tank andfrom here it eventually passes to the polyalkylene polyamine reactor.

In a preferred embodiment of the invention,hexamethylenetetramine-inorganic nitrate explosive slurry can, forexample, be prepared in accordance with the following procedure.

To prepare a hexamethylenetetramineammonium nitrate slurried explosivecomposition, formaldehyde and ammonium nitrate are mixed and reacted inaqueous solution in stoichiometric proportions at a temperature withinthe range from about 15 C. to about 250 C. If the resulting slurriedexplosive is to be based on ammonium nitrate alone, or together withanother inorganic nitrate as the inorganic oxidizer, then the ammoniumnitrate can be used in an amount in excess of that stoichiometricallyrequired to form hexamethylenetetramine, and in a sufficient amount toprovide the desired amount of ammonium nitrate in the finished slurriedexplosive. The reaction is carried out in the presence of suflicientbase, usually from 0.05 to 10% by weight of the solution, to ensure theformation of the hexamethylenetetramine and inhibit formation ofmethyleneimine, in accordance with the known reaction procedure.

These reactants are capable of forming lower and also higherpolyalkylene polyamines, depending upon the relative proportions offormaldehyde and ammonia in the reaction mixture.

By the use of organic ammonia compounds and amines, substitutedhexamethylenetetramine derivatives are obtained, the substituents ofwhich correspond to the organic radical of the organic ammonia compoundor amine. Thus, for example, formaldehyde and isobutyl amine formtriisobutyltrimethylenetriamine, a substituted trioxymethylene.

After completion of the formation of the polyalkylene polyamineexplosive sensitizer, additional components can be added to form thedesired slurried explosive, in proportions to ensure oxygen balance,good explosive power, and sensitivity to detonation. In addition to thepolyalkylene polyamine explosive sensitizer, any unreacted ammoniumnitrate, formaldehyde and methanol, the slurried explosives inaccordance with the invention will usually include an inorganicoxidizer, a fuel, and, if desired, thickening agents, and emulsifyingagents, as desired, to ensure a homogeneous mixture at the blastingsite.

The oxidizer employed can be an inorganic nitrate. Ammonium nitrate, andnitrates of the alkali and alkaline earth metals, such as soduimnitrate, potassium nitrate, calcium nitrate, magnesium nitrate,strontium nitrate and barium nitrate, are exemplary inorganic nitrateswhich can be mixed into the reaction mixture. Ammonium nitrate andmixtures of ammonium nitrate and another nitrate are preferred.Excellent results are obtained with mixtures of ammonium nitrate andother inorganic nitrates, and such mixtures are frequently preferredover a single nltrate.

As an inorganic oxidizer to be mixed into the reaction mixture there canalso be used a chlorate or a perchlorate of an alkali or alkaline earthmetal, such as sodium chlorate, potassium chlorate, barium chlorate,sodium perchlorate, potassium perchlorate, barium perchlorate, andcalcium perchlorate, mixtures of nitrates, chlorates and perchlorates,of nitrates and perchlorates, and one of chlorates and perc-hlorates.

When mixtures of ammonium oxidizer and the other oxidizer are used, therelative proportion of ammonium oxidizer is important for good explosiveshock and power. The ammonium oxidizer is employed in a proportionwithin the range from about 50 to 95% by weight of the total oxidizer,and the other oxidizer or oxidizers in the proportion of from about 5 toabout 50% of the total oxidizer. For optimum power, the proportions arefrom to ammonium oxidizer, and from 10 to 20% other oxidizer oroxldizers. The proportions of oxidizers selected within these rangeswill depend upon the sensitivity and explosive effect desired and thesein turn are dependent upon the particular oxidizer used.

The inorganic oxidizer can be fine, coarse, or a blend of fine andcoarse materials. Mill and prill inorganic oxidizers are quitesatisfactory. For best results, the inorganic oxidizers should befine-grained.

The relative proportions of the explosive sensitizer and oxidizer whenused in the explosive composition formed by the process of the inventionwill depend upon the sensitivity and explosive power desired, and thesein turn are dependent upon the particular oxidizer and explosivesensitizer. For optimum effect, the oxidizer is used in an amount withinthe range from about to 75%, and the explosive sensitizer in an amountwithin the range from about 5 to about 40%, by weight of the explosivecomposition. From about to about explosive sensitizer and from about 50to 70% oxidizer give the best results.

In addition to these materials, the explosive compositions of theinvention can include a fuel, when needed, which can be mixed into theexplosive composition. The fuel can be either a metal fuel of acarbonaceous fuel, in an amount of from about 0.5 to about 30%.Formaldehyde and methanol are very satisfactory fuels. Additionalcarbonaceous fuels include powdered coal, petroleum oil, coke dust,charcoal, bagasse, dextrine, starch, Wood meal, wheat flour, bran, pecanmeal, and similar nut shell meals. The carbonaceous fuel will usually beused in an amount Within the range from 0.5 to about 20%.

Satisfactory metal fuel include aluminum, which can be in the form ofpowder or flake, or in a very finelydivided form known as atomizedaluminum, ferrosilicon and ferrophosphorus. The metal fuel will usuallycomprise from about 0.5 to about 15% of the composition.

The preferred slurrying liquid, as indicated previously, is water.Methanol will also serve. Other slurrying liquids also can be used, andamong such organic liquids, polyhydric alcohols, petroleum oil andliquid hydrocarbons are preferred for many uses.

The amount of slurrying liquid is always enough to act as a suspendingmedium for the solid ingredients, and facilitate their conveyance to theblasting site. Consequently, following the addition of additional solidingredicuts to the reaction mixture in forming the finished explosiveslurry, it may in many cases be necessary to add additional slurryliquid to act as a suspending medium for the additional solidingredients. Usually, 7% liquid is sufiicient to barely slurry a mixtureof the desired type, but much more may be required to make the slurrysufficiently flowable. The practical upper limit is set only byexcessive dilution and reduction in sensitivity, together withdissipation of the explosive power. In most cases, the preferred rangeof slurrying liquid is from 10 to although in some cases, as much as 50%can be used. In these proportions, t-he.viscosity of the finished slurryis, of course, a factor to be taken into account.

In the case of oils, any oil can be used as the suspending medium.Petroleum-derived hydrocarbon oils are readily available, and arepreferred because of their low cost. The viscosity can range from verythin, such as 50 SSU at 100 F., to quite heavy oils, up to about 1200SSU at 100 F. Kerosene, fuel oil, 100 SSU parafiin oil, light strawparafiin oil, SAE 10 to 50 lubricating oils, and hydraulic oils areexemplary.

The consistency of the slurry for any given amount of suspending liquidcan be increased to meet any need by incorporating a thickening orgelatinizing agent for thickening the slurrying liquid. In this way, itis possible to prepare thin or thick slurries, containing a largeproportion of suspending liquid. The thickener can be prepared for useas an alkaline medium, if the reaction mixture obtained in the inventionis alkaline.

When relatively large proportions of water are present, water-soluble orwater-dispersible thickeners can be added,

, 5 for example, such as carboxymethyl cellulose, methyl cellulose, guargum, psyllium seed mucilage, and pregelatinized starches, such asHydroseal 3B. The amount of such thickening agent will depend upon thedesired consistency, and usually will be within the range from 0 toabout 5%.

Noncarbonaceous inorganic oil thickeners useful in making thickened oilsand greases, such as finely-divided silica, available under the tradename Cab-O-Sil and Ludox, and silica aerogels, for example Santocel ARDand Santocel C, and like inorganic gelling agents, such as alumina,attapulgite, and bentonite, can be used. Other gelling agents aredisclosed in US. Patents Nos. 2,655,476 and 2,711,393. These are wellknown materials, and any of these known in the art can be used. Theamount of such thickening agent will depend on the consistency desired,and usually will be within the range from 0 up to about 5 Enoughthickener can be added to gel the oil after loading into the bore holeor other blasting site, if desired, and waterproofing agents such as aredisclosed in US. Patents Nos. 2,554,222, 2,655,476 and 2,711,393, can beincorporated as well, to impart water resistance to the gelled slurry.

The finished slurry is readily prepared by simple mixing of theadditional ingredients which are to be incorporated with the explosivesensitizer reaction mixture. The solid materials, including theinorganic nitrate, fuel and thickener, if any, would usually be mixedfirst, to form a homogeneous blend, which is then incorporated in thesensitizing reaction mixture, together with sufi'icient additional oiland Water, and thickener, if required, to bring the mixture to thedesired consistency, which can range from a gelled thix-otropic oil orthick, barely pourable mixture, to a quick-flowing liquid.

The explosive slurry can be fired (after filling into the blasting siteor bore hole) with the aid of a booster charge, and preferably underhigh confinement. Any conventional booster charge available in the artcan be employed, of which pentaerythritol tetranitrate and pentolite areexemplary. The booster can be lowered into the bore hole before or afterloading the explosive slurry.

In formulating the finished explosive, the blasting site requirementswill of course be taken into account. Thus, a rather thick slurry can beformulated for use in wet bore holes, in which the water can be expectedto considerably dilute the slurry after loading. Alternatively,waterproofing agents can be incorporated in the slurry, so as to resistdilution thereof by water present in the hole. Those skilled in the artwill appreciate the variations that will be required to ensuredetonation under the required conditions.

The drawing shows apparatus which can be used in carrying out theabove-described process.

The apparatus shown in the figure comprises a reactor 10 incommunication with a slurry mixer 34 via conduit 36. The reactor 10 isequipped with a stirrer 14, operated by motor 13, and with a temperaturecontrol jacket 20. A suitable feeder 38, such as a vibrator, is attachedto conduit 36 for uniformly and controllably delivering the explosivecomposition from the reactor to the slurry mixer. A third tank 40 forstoring slurry liquid is in communication with the slurry mixer by meansof a pipe 42 which contains valve 44 and pump 41. A second pump 48 is incommunication with the slurry mixer, for transporting explosive slurryfrom the mixer to the bore hole or other blasting site.

In operation, raw materials, for example, formaldehyde and ammoniumnitrate, are fed from the storage tanks 22 and 24, through conduits 26and 28 respectively, and solid or aqueous base, such as sodium hydroxidepellets or solution, are fed from tank 26 via chute 27 at apredetermined rate into the reaction tank 10, wherein the raw materialsare mixed by mixer 14 and reacted to form an explosive composition ofhexamethylene tetramine and ammonium nitrate, as well as formaldehyde,if this is in excess; this is a fuel. As the explosive composition isformed in the reactor 10, it is fed into the slurry mixer 34, along withslurrying liquid from the slurrying liquid storage tank 40, mixed in theslurry mixer 34, and thereafter pumped via pump 48 to the bore hole orother blasing site. A feed hopper 35 is provided for additionalmaterials to be included in the slurry, such as gums and otherthickeners.

The formaldehyde can be obtained as a formalin solution, and used assuch. The apparatus as shown, however, includes apparatus formanufacturing formaldehyde from methanol and air. The air is suppliedvia pump 1 and filter 2 to the mixer and vaporizer 4, where methanol isfed in by gravity from reservoir 3. The gaseous mixture from thevaporizer is led to preheater 5, where it is brought to about 450 C. andthen led into the reactor 6 which contains a silver catalyst bed. Thereactor is held at 450 to 650 C., preferably 635 C. The reaction mixtureis then pumped into the storage reservoir 7, when the mixture of 28 to30% formaldehyde and 20 to 22% methanol is dissolved in water to form a20 to 37% solution of formaldehyde, with accompanying methanol. Themethanol is a fuel, and hence is not separated, since it is a valuableadjunct in the final explosive. In this case, the final slurry thus alsocontains methanol, and can contain formaldehyde, which is also a fuel.

The following examples, in the opinion of the inventor, represent thebest embodiments of this invention.

Example 1 A hexamethylenetetramine-ammonium nitrate explosivecomposition was prepared at the blasting site using the apparatus shownin the figure. An aqueous 30% solution of formaldehyde was fedcontinuously with an aqueous ammonium nitrate solution providing 27%aqueous ammonia, with sodium hydroxide, in a weight ratio HCHO:NH of4:3, at a temperature of about 30 C. The resulting solution contained40% solids, and was concentrated at 60 to 70 C. to form a heavy slurrycontaining hexamethylenetetramine and ammonium nitrate.

The slurry was readily pumped into a two inch blast hole. When detonatedwith one pound pentolite primers, it detonated completely, with goodrock breakage.

Example 2 The slurry of Example 1 was blended in the mixer 34 withadditional ammonium nitrate, aluminum metal, and guar gum to give afinal slurry of the composition:

Parts by wt. Hexamethylenetetramine 4.0 NH N0 65.0 Al (granular) 20.0Guar gum 0.4 Water 10.6

The slurry was pumped into a four inch bore hole. It detonated readilywith 1 pound pentolite primers, spaced every four feet, with good rockbreakage.

Example 3 A mixture of one volume of air and one volume of methanolvapor was fed in the apparatus of the figure to a reactor at 635 C. andconverted by the silver catalyst to a mixture of formaldehyde andmethanol containing a ratio of HCHO:CH OH of 15:11. This was dissolvedin a 73% aqueous ammonium nitrate solution containg 12% sodiumhydroxide, to produce a solution containing 30% HCHO, at a 2.521 ratioof HCHO:NI-l as aqueous NH This solution was reacted as in Example 1 toyield an aqueous hexamethylenetetramine ammoniumnitrateformaldehyde-methanol solution, containing:

Parts by wt. Hexamethylenetetramine 4.0 NH NO 65.0 HCHO 2.0 cn on 3.0

Water 23.0

To this was added 0.5 part of guar gum. The solution was then pumpedinto a bore hole, where it was detonated using 1 pound pentolite primersevery four feet, with good rock breakage.

Example 4 To the slurry-reaction mixture of Example 3 there were added20 parts wet nitrostarch containing about 23% water, and 0.5 part guargum. The solution was then pumped into a bore hole, where it wasdetonated using 1 pound pentolite 10 primers every four feet, with goodrock breakage.

Exiample 5 To the slurry-reaction mixture of Example 3 there were added20 parts Wet TNT containing about 23% water, and 0.5 part guar gum. Thesolution was then pumped into a bore hole, where it was detonated using1 pound pentolite rimers every four feet, with good rock breakage.

Example 6 To the slurry-reaction mixture of Example 3 there were added20 parts wet 4:1 nitrostarch-DNT mixture containing about 23% Water, and0.5 part guar gum. The solution was then pumped into a bore hole, whereit was detonated using 1 pound pentolite primers every four feet, withgood rock breakage.

Having regard to the foregoing disclosure, the following is claimed asthe inventive and patentable embodiments thereof:

1. A method of blasting using polyalkylene polyamine sensitizedexplosives made in situ proximate to the blasting site from nonexplosivestarting materials, which comprises mixing and reacting formaldehyde andan antmonium containing compound forming a polyalkylene polyamine in aninert reaction medium which desensitizes the polyalkylene polyamineexplosive sensitizer formed as a reactant product, thereby forming areaction mixture comprising the explosive polyalkylene polyaminesensitizer, incorporating in the mixture additional formulatingcomponents, if necessary, to form an explosive composition comprisingthe explosive sensitizer, an oxidizer, and a fuel in amounts tooxygen-balance the mixture and ensure detonation, delivering thecomposition to the blasting site, and detonatin g the composition.

2. A method as in claim 1 wherein the reactants are formaldehyde andammonium nitrate and form hexamethylenetetramine.

3. A method as in claim 1 which comprises incorporating excessammonium-containing compound in the reaction mixture, to form anexplosive composition including such compound as the oxidizer.

4. A method as in claim 1 in which the ammonia-containing compound isammonium nitrate.

5. A method as in claim 1 which comprises incorporating aluminum in theexplosive composition as an additional formulating component.

6. A method as in claim 1 which comprises incorporating a fuel in theexplosive composition as an additional formulating component.

7. A method as in clairn 1 including the step of concentrating thereaction mixture to form a slurried explosive composition for deliveryto the blasting site.

8. A method as in claim 1 wherein the reaction medium is an aqueousreaction medium.

References Cited UNITED STATES PATENTS 2,976,137 3/1961 Stengel 14946 X3,075,464 1/1963 Woodle et al. 10223 3,127,835 4/1964 Alexander 102-23BENJAMIN A. BORCHELT, Primary Examiner.

V. R. PENDEGRASS, Assistant Examiner.

1. A METHOD OF BLASTING USING POLYALKYLENE POLYAMINE SENSITIZEDEXPLOSIVES MADE IN SITU PROXIMATE TO THE BLASTING SITE FROM NONEXPLOSIVESTARTING MATERIALS, WHICH COMPRISES MIXING AND REACTING FORMALDEHYDE ANDAN ARMMONIUM CONTAINING COMPOUND FORMING A POLYLALKYLENE POLYAMINE IN ANINERT REACTION MEDIUM WHICH DESENSITIZES THE POLYALKYLENE POLYAMINEEXPLOSIVE SENSITIZER FORMED AS A REACTANT PRODUCT, THEREBY FORMING AREACTION MIXTURE COMPRISING THE EXPLOSIVE POLYALKYLENE POLYAMINESENSITIZER, INCORPORATING IN THE MIXTURE ADDITIONAL FORMULATINGCOMPONENTS, IF NECESSARY, TO FORM AN EXPLOSIVE COMPOSITION COMPRISINGTHE EXPLOSIVE SENSITIZER, AN OXIDIZER, AND A FUEL IN AMOUNTS TOOXYGEN-BALANCED THE MIXTURE AND ENSURE DETONATION, DELIVERING THECOMPOSITION TO THE BLASTING SITE, AND DETONATING THE COMPOSITION.